A prospective randomized controlled study of liver-directed and systemic adjuvant therapy in patients with high risk colon (excluding rectal) cancers is being carried out by the Gastrointestinal Tumor Study Group. Patients are randomized to no adjuvant therapy or to 2100 R of liver irradiation combined with 3 days of IV 5-FU. Forty patients have been entered since the study was begun in August, 1979. No conclusions regarding efficacy can be made at this early data. Myelosuppression has been more striking than expected and, though no deaths have occurred, the 5-FU dose has been modified.